This invention relates to an improved apparatus and method of analyzing the chemical structure of a specimen utilizing nuclear magnetic resonance ("NMR") techniques. A resonance domain having a selectable size is moved in a discrete cross sectional grid pattern with respect to the specimen to scan the specimen. NMR signals are generated at discrete grid locations during scanning which signals are detected and processed to form a map showing the location and an indication of the quantitative amount of selected nuclei present at such location. By suitable rearrangement of the apparatus, sagittal and frontal sectional maps may also be produced.
This invention is an improvement of the apparatus and method described in U.S. Pat. No. 3,789,832 to Raymond V. Damadian (the '832 patent). As described in the '832 patent, it was discovered that cancerous cells had chemical structures different from normal cells. A method and apparatus were described in the '832 patent of measuring certain NMR signals produced from a specimen and comparing these signals with the NMR signals obtained from normal tissue to obtain an indication of the presence, location and degree of malignancy of cancerous tissue within the specimen.
The use of NMR techniques to analyze materials including living tissue has been an active field since the issuance of the '832 patent. For example, see "Medical Imaging by NMR" by P. Mansfield and A. A. Maudsley, British Journal of Radiology, Vol. 50, pages 188-194 (1977); "Image Formation by Nuclear Magnetic Resonance: The Sensitive-Point Method" by Waldo S. Hinshaw, Journal of Applied Physics, Vol. 47, No. 8, August, 1976; "Magnetic Resonance Zeugmatography" by Paul C. Lauterbur, Pure and Applied Chemistry, Vol. 40, No. 1-2 (1974); U.S. Pat. No. 4,015,196 to Moore et al.; and U.S. Pat. No. 3,932,305 to Abe et al.
These references include discussion of various methods of analyzing a specimen utilizing NMR techniques. All of these methods, however, have a major disadvantage in that the magnetic field for generating NMR signals cannot be focused to adjust the size of the resonance domain depending on the particular user requirements which might occur, for example, when a macroscopic scan of a specimen is desired instead of a microscopic scan.
The inventor here has published several articles on the general subject of utilizing field focusing NMR techniques. See "Tumor Imaging In A Live Animal By Field Focusing NMR (FONAR)", Physiological Chemistry and Physics, Vol. 8, pages 61-65, (1976); "Field Focusing Nuclear Magnetic Resonance (FONAR): Visualization of a Tumor in a Live Animal", Science, Vol. 194, pages 1430-1432 (Dec. 27, 1976); "Nuclear Magnetic Resonance: A Noninvasive Approach to Cancer", Hospital Practice, pages 63-70 (July, 1977) and "NMR in Cancer: XVI. Fonar Image of the Live Human Body" by R. Damadian et al., Physiological Chemistry and Physics, Vol. 9, No. 1 (1977). There has also appeared in article "Damadian's Super Magnet and How He Hopes To Use It To Detect Cancer" by Susan Renner-Smith in Popular Science, pages 76-79, 120, (December, 1977).